In the past thermoelectric devices have included thermopiles made up of thermoelectric couples (thermocouple). Each thermocouple consists of a bar of P-type semiconductor material and a bar of N-type semiconductor material. An electrode connects one end of the P-type bar and one end of the N-type bar. The N-type bar of one thermocouple is connected to the P-type bar of the next thermocouple to form the thermopile.
The disadvantages of using bars of P-type and N-type semiconductors as the elements of the thermocouple are as follows:
(1) the bars are sawed from plates and a substantial amount of the material is lost in the form of saw dust; (2) the bars are brittle and fragile and thus their use is restricted to nonflexible type thermocouples; and (3) although the bars may be considered small in size, they cannot be made small enough for use in connection with all applications presently available in the market-place.